1996 Four Winns Sundowner with 5.0 Cobra engine and drive

[Lou C]

getting back to that anti-siphon valve....from US Coast Guard Regs....
https://www.law.cornell.edu/cfr/text/33/183.568
other good things to know, relating to engine compartment ventilation for inboard gas engines, etc:

33 CFR Part 183 - PART 183—BOATS AND ASSOCIATED EQUIPMENT

www.law.cornell.edu

 

[Lpgc]

getting back to that anti-siphon valve....from US Coast Guard Regs....
https://www.law.cornell.edu/cfr/text/33/183.568
other good things to know, relating to engine compartment ventilation for inboard gas engines, etc:

33 CFR Part 183 - PART 183—BOATS AND ASSOCIATED EQUIPMENT

www.law.cornell.edu

Thanks Lou, I opened the links...

Copied and pasted...

§ 183.568 Anti-siphon protection.
Each fuel line from the fuel tank to the fuel inlet connection on the carburetor must:

(a) Be above the level of the tank top; or

(b) Have an anti-siphon device or an electrically operated fuel stop valve:

(1) At the tank withdrawal fitting; or

(2) Installed so the line from the fuel tank is above the top of the tank; or

(c) Provided that the fuel tank top is below the level of the carburetor inlet, be metallic fuel lines meeting the construction requirements of § 183.538 or “USCG Type A1” hose, with one or two manual shutoff valves installed as follows:

(1) Directly at the fuel tank connection arranged to be readily accessible for operation from outside of the compartment, and

(2) If the length of fuel line from the tank outlet to the engine inlet is greater than 12 feet, a manual shutoff valve shall be installed at the fuel inlet connection to the engine.

[CGD 74-209, 42 FR 5950, Jan. 31, 1977, as amended by CGD 81-092, 48 FR 55737, Dec. 15, 1983; CGD 85-098, 52 FR 19729, May 27, 1987]

===========

a - the fuel line comes out the top of the tank and the carb is definitely above the fuel tank? Not sure if the rubber fuel line is all above fuel tank level and I know that if it were to come off the fuel filter it could/would dangle so it would be below the level of the top of the fuel tank.

I don't see how the design of the valve could prevent siphoning in the even the rubber hose came off the filter and dangled below top of fuel tank level? It could be designed to limit the flow (if the hole the ball sits in gets narrower toward the output side, which is something I haven't checked) but I don't see how it would shut off if a certain flow limit were exceeded. It also occurs to me that if the boat does 1mpg flat out and does 45mph flat out this equates to flow of around 1 gallon every 80 seconds or 1 pint every 10 seconds, which is around what I'd expect if the tank were full and the rubber hose were siphoning fuel into the lowest part of the bilge - how would an ant-syphon valve know if that fuel were being pumped to the carb or just flowing into the bilge if the suction on the valve is around the same if the boat is driven flat out or if the rubber hose has come off and is siphoning fuel into the bilge?

Or maybe I'm wrong and it would siphon much faster than 1 gallon every 80 seconds if the pipe came off and the tank were full? But for the anti-syphon valve to not risk shutting off fuel to the carb if the boat is driven flat out the siphoning would have to be much quicker than 1 gallon every 80 seconds?

 

[Lou C]

The only time the ball valve opens is when suction from the pump, pulls against the spring pressure. When the pump quits pumping the spring is supposed to close the ball valve to shut off the flow of fuel.
Your question of what would happen if the fuel line leaked with the engine running vs with the engine off is a good one. I think what might happen is this, engine off, no vacuum on the fuel in the line, valve will stay closed.
Engine on, if the line leaks, air will also enter the line, reducing vacuum against the fuel in the line, and (HOPEFULLY) the valve will close and prevent an explosion!

 

[Lpgc]

Ahh now I understand, thanks.

I previously thought it was being described as an excess flow shutoff valve. I was thinking the engine at full throttle could suck fuel at around the same speed as fuel would siphon out of the rubber pipe if the rubber pipe became disconnected from the filter and just dangled into the bilge below fuel tank level, so an excess flow valve couldn't be used to prevent such siphoning or it would also limit flow to the engine at full throttle... But I get it now and understand it's an anti-syphon valve.

Will also have the effect of preventing fuel flowing backwards from the filter to the tank... I know that wouldn't happen with the engine running but I don't know if it could happen with the engine off if the valve wasn't fitted?

 

[Lou C]

I think so, because there is no vacuum against the ball valve with the engine off.

 

[Lpgc]

I think so, because there is no vacuum against the ball valve with the engine off.

Yes, I was thinking there'd be some siphon suck on the valve if the rubber hose full of fuel came off the fuel filter and hung down in the bilge... But now I see maybe not enough suck to open the valve.

 

[Lpgc]

Not boat related but a few people were interested in the other car I recently worked on... I'm currently converting this 1972 Chevy pickup to run on LPG (propane)

 

[Lou C]

Love the Alabama plate on the Chevrolet. Those trucks were everywhere when I was growing up. In our town in suburban Westchester NY, Ford was on one side of the street and Chevrolet was on the other side. My friend's dad was the Ford shop foreman so I got to check out all the cool cars they worked on at the dealership. Like Boss 302 Mustangs, Torino Cobras with 429s, etc. Plus his family was into restoring cars before it was fashonable (that came later, like after the movie American Grafitti came out in 1973) and he built a '23 T-Bucket hot rod from a kit when we were in high school. This thing showed up at his home in 5 big boxes, steel frame, fiberglass body, and he powered it with a 302 cu in Ford, C-4 auto trans and of course, a Ford 9" rear end. That, was the coolest car in my neighborhood. I "think" some of the parts, may have come from warrantee returns at the dealership, but not sure if I am remembering that right, because it was more than 50 years ago!
I was driving a 1969 Fiberfab Dune Buggy then built off of a 1956 VW Beetle with a 1200 cc 40 hp VW flat four. Biggest job I did on that car was to re-wire the whole thing because nothing worked! It was just like the wiring in a boat, because the body was fiberglass, so you were supposed to use bus bars for grounding points, of course I didn't know that being only 17 years old so came up with my own solution for grounding all the lights, etc. Just grounded the front lights to the front frame head and the rear ones to a convenient point on the rear frame. Lucky it was a very simple system with maybe 8 circuits (6 volt).After that, everything worked, that job taught me about simple DC wiring. Wish I still had it. It had a top, side curtains and a VW heater, but will still tough to drive in winter.